Puff pieces: Sculptures made of thin air

Nimbus D' Aspremont by Berndnaut Smilde, part of ManifestlyPresent at Aspremont-Lynden Castle, Lanaken, Belgium, from 3 June to 30 September

FORGET about planetary-scale geoengineering: seeding clouds indoors is taking the world by storm.

To achieve this feat of ephemeral sculpture, Dutch artist Berndnaut Smilde mists water in the air with a plant spray bottle, releases a burst of "fog" - actually a vaporised glycol-based compound - from a smoke machine, and employs backlighting to show off the resulting cloud to perfection.

"The moisture sticks to the smoke and makes the smoke heavier, otherwise it would just rise and fall apart," Smilde says. The effect works best in a cold, damp room. "When the floor and walls are a bit wet, [the moisture] gets in the air of the whole space and it helps."

Making clouds indoors is an imprecise art. "It takes a lot of practice and there's a lot of coincidence involved," Smilde says. "You have to test it and see whether it works."

Each cloud only lasts for a few seconds. Why go to all that trouble to produce a sculpture that just vanishes in thin air?

"I was curious if it was possible to exhibit a raincloud," Smilde says, "and I really like the impermanent aspect of it. Also, if you put a natural situation in an unnatural space, it feels a bit threatening, a bit confrontational."

For me, it is the very temporary nature of the indoor cloud that makes it enchanting, tantalising and somehow endearing. In online videos of Smilde at work, the onlookers appear rapt with joy, as if watching a fireworks display for the first time.

Created in castles and gallery spaces, the clouds are photographed for posterity. One example is the image above, being shown at the ManifestlyPresent exhibition in a castle in Belgium. "It's about this very short moment in time, a specific location," Smilde says. "It's almost like a memory of this cloud that happened there."